FIG. 1 illustrates a typical track-laying vehicle 1 having a chassis and frame 3 with a longitudinal axis A--A, an operator's cabin 4, and an engine 2. Although the vehicle is shown with loader arm 5, the principles that are presented in this specification will equally apply to a tracked vehicle, which is used for other operations routinely associated with track-laying vehicles such as pushing large loads.
As used in this specification, the term "external" refers to an object that is of, relates to, or connected with the external limits of the track-laying vehicle.
Track-laying vehicle 1 is propelled by at least one endless track 8 that runs along each longitudinal side of chassis 3. (For clarity, the track mounted on the opposite side of the vehicle is not shown.) Track 8 is trained around and supported by the treads on the leading side of front wheel 9 and the treads on the lagging side of rear wheel 10. Wheels 9 and 10 are typically pneumatic tires and at least one is a driven wheel, and as used here "driven" means that, absent track 8, the wheel is still mechanically or hydraulically connected to motor 2. When functioning properly, track 8 maintains lateral registry with wheels 9 and 10 due to the presence of lugs 11 that extend inwardly against the sidewalls of wheels 9 and 10 from both the inside and the outside edges of track 8. Track 8 is preferably constructed of metal such as steel or an elastomeric material such as rubber.
The track-laying vehicle described to this point is widely known and commercially available from such sources as Case Corporation located at 700 State Street, Racine, Wis. 53404, United States of America. Vehicles such as these can be ordered with the tracks installed or the tracks may be purchased separately and added to the vehicle later.
Regardless of when the tracks are installed, typically the supporting structure for wheels 9 and 10 is not fully designed to operate with track 8 in place. Track 8 tends to pull wheels 9 and 10 together, disrupting the wheels' coplanar alignment, which can eventually deform the structure that supports the wheels and cause wheels 9 and 10 to operate at something less than 180 degrees apart. In other words, the shafts upon which wheels 9 and 10 are mounted permanently deflect toward each other and force wheels 9 and 10 to rotate in separate planes.
This misalignment can cause track 8 to prematurely fail. The sidewalls of wheels 9 and 10 excessively rub against the inside of lugs 11 as track 8 travels around the wheels. This rubbing causes lugs 11 to flex inward and outward, which over time, weakens track 8 to a point where lugs 11 flip-up and track 8 rolls off wheels 9 and 10.
What is needed is a device that maintains wheels 9 and 10 in proper alignment when track 8 is used. This invention is one solution to that need.